Container having meta-stable panels

ABSTRACT

A container has meta-stable panels to compensate for internal vacuum from hot filling. The panels include a groove that yields during deformation such that the stiffness of the panel varies from its pre-yield stage to its post-yield stage.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. provisional application No.60/895,288 filed Mar. 16, 2007, which is incorporated by referenceherein in its entirety.

BACKGROUND

The present invention relates to the structure and function ofcontainers, and more particularly to containers capable of receiving hotfluids and having panels capable of inward deflection, and methodsrelating to same.

Perishable beverage and food products are often placed into containersat elevated temperatures. In a conventional hot-fill process, the liquidor flowable product is charged into a container at elevatedtemperatures, such as 180 to 190 degrees F., under approximatelyatmospheric pressure. Because a cap hermetically seals the productwithin the container while the product is at the hot-fillingtemperature, hot-fill plastic containers are subject to negativeinternal pressure (that is, relative to ambient pressure) upon coolingand contraction of the products and any entrapped air in the head-space.The phrase hot filling as used in the description encompasses filling acontainer with a product at an elevated temperature, capping or sealingthe container, and allowing the package to cool.

It has been a goal of conventional hot-fill container design to formbodies that have a desired and predictable shape after hot filling. Forexample, containers having an approximately cylindrical body or acircular transverse cross section, the goal has been to retain the shapeafter the hot filling process. To promote this goal, conventionalhot-fill containers include designated flexing portions—vacuumpanels—that deform when subjected to typical negative internal pressuresresulting from the hot filling process. The inward deflection of thevacuum panels tends to equalize the pressure differential between theinterior and exterior of the container to enhance the ability of thecylindrical sections to maintain an attractive shape, to enhance theease of labeling, or provide like benefit.

Some container designs are symmetric about a longitudinal centerline anddesigned with stiffeners to maintain the intended cylindrical shapewhile the vacuum panels deflect. For example, U.S. Pat. Nos. 5,178,289;5,092,475; and 5,054,632 teach stiffening portions or ribs to increasehoop stiffness and eliminate bulges while integral vacuum panelscollapse inwardly. U.S. Pat. No. 4,863,046 is designed to providevolumetric shrinkage of less than one percent in hot-fill applications.

Other containers include a pair of vacuum panels, each of which has anindentation or grip portion enabling the container to be gripped betweena user's thumb and fingers. For example, U.S. Pat. No. 5,141,120 teachesa bottle having a hinge continuously surrounding a vacuum panel, whichincludes indentations for gripping. In response to cooling of thecontainer contents, the hinge enables the entire vacuum panel tocollapse inwardly.

For most conventional hot fill bottles, a graph of internal pressure vs.volumetric displacement in response to internal vacuum is a straightline. Some references disclose vacuum panels in hot fill containershaving portions that invert from an outwardly bulged state to aninwardly bulged state during the deflection process. For example, U.S.Pat. No. 5,141,121 discloses a vacuum panel having an outwardly bulgedsurface that inverts relative to a vertical plane in response tointernal vacuum. U.S. patent application Ser. No. 10/361,356 (Lane)discloses a vacuum panel for a hot fill container having a compoundcurve and indents. A central portion of the vacuum panel inverts toproduce a sharp downward deviation in the graph of internal vacuumversus volume displacement represented in FIG. 7 of the 356 application.Outside of the panel inversions, the graph of FIG. 7 of the 356application is a series of straight lines that appear to shareapproximately the same slope.

SUMMARY

As plastic blow-molded bottles are engineered to decrease their weight,new vacuum panel technology is required. Accordingly, a container havingat least one metastable volume compensation panel is provided. Themetastable panel may have a first stiffness, undergoes a buckling orlike phenomenon, and has a second stiffness after buckling. Preferably,the buckling (or the like phenomenon) occurs in a local or small areaand enables the change in stiffness.

A plastic bottle suitable for hot-filling comprises an enclosed circularbase; an upper portion including an opening; and a body disposed betweenthe base and the upper portion. The body includes a sidewall and atleast one volume compensation panel that generally deflects inwardly inresponse to negative pressure after hot filling, such that during apre-yielding stage, the vacuum panel deflects inwardly at a firststiffness and, during a post-yielding stage, the vacuum panel deflectsinwardly at a second stiffness. Preferably, a portion of the panelyields during the inward deflection, thereby facilitating a change instiffness, and the first stiffness does not equal the second stiffness.Preferably, the yielding stage includes buckling.

Each panels may include a groove disposed between a pair of fields. Inthis configuration, a portion of the groove slowly gives way during saidinward deflection, thereby facilitating the stiffness variation, or aportion of the groove buckles during said inward deflection, therebyfacilitating the stiffness variation. Each panel may also include a pairof opposing rim walls, a pair of raised fields disposed within saidedge, and a groove disposed between the fields. The rim walls is locatedproximate a corresponding edge of the body sidewall.

The bottom the groove is higher than a bottom of the rim walls, and eachone of an uppermost portion of the fields is higher than the bottom ofthe groove. The grove has a pair of opposing end walls that extendinwardly from the groove bottom to the rim walls, and the groove extendsapproximately from one of the rim walls approximately to the opposingrim. In some configurations, the end walls buckle in response to thenegative pressure. Often, it is the buckling that enables inwardmovement of the groove.

According to another embodiment, a plastic bottle suitable forhot-filling comprises an enclosed circular base; an upper portionincluding an opening; and a body located between the base and the upperportion. The body includes a sidewall and at least two volumecompensation panels that deflect inwardly after hot-filling. Each one ofthe panels includes an upper field, a lower field, and a rib that isdisposed between the upper and lower fields and that includes an obliqueportion that buckles during the volume compensation process. Thebuckling facilitates inward movement of the upper and lower fieldschanges the stiffness from a pre-buckling value to a post-bucklingvalue. Preferably, the oblique portion of the rib is located at an endof a bottom of the rib and forms an oblique angle with a bottom of therib and is not tangential to the body sidewall. Preferably, the rib hassidewalls that extend upwardly from the rib bottom and connect to thefields, which have an approximately flat surface.

According to another aspect of the invention, a method of absorbingnegative pressure within a hot-filled plastic bottle comprises the stepsof providing a bottle and filling the bottle with a liquid product at anelevated temperature and sealing or capping the opening. The bottle hasan enclosed circular base; an upper portion including an opening; and abody located between the base and the upper portion. The body includes asidewall and at least two volume compensation panels, as generallydescribed above. The method also includes that at least a portion of thepanels deflect inwardly after the filling and sealing step in responseto negative pressure within the bottle. The inward deflection includes afirst main stage wherein the volume compensation panels exhibit a firststiffness and a second main stage wherein the volume compensation panelsexhibit a second stiffness.

According to another embodiment, a plastic bottle suitable for ahot-filling process in which internal vacuum is created comprises anenclosed circular base, an upper portion including an opening; and abody located between the base and the upper portion. The body includes asidewall and at least one volume compensation panel that generallydeflects inwardly in response to vacuum after hot filling. The panel hasan upper field, a lower field, and a hinge located between the upper andlower fields, such that deformation of the panel in response to vacuumoccurs in a first stage, a transition stage after the first stage, and asecond stage after the transition stage; such that: (i) in the firststage the upper field and lower field are gradually drawn inwardly inresponse to vacuum; (ii) the transition stage is unstable such that atleast a portion of the panel jumps from the first yielding stage to thesecond yielding stage; and (iii) in the second yielding stage the upperfield and lower field are gradually drawn inwardly in response tovacuum.

For this embodiment, preferably, each of the upper field and the lowerfield have an inner end located proximate the hinge and an outer endlocated distal from the hinge, and the inward deformation of each fieldinner end is greater than the deformation of the each field outer end.Also preferably, the inward deformation of each field inner end isgreater than the deformation of the each field at its longitudinalcenter. And wherein, in longitudinal cross section, a line between theupper field outer end and the upper field inner end forms an internalangle with a line between the lower filed outer end and the upper fieldinner end, and the angle is less than 180 degrees. This angle may go toapproximately 180 degrees or more after vacuum deformation is complete.

Preferably, the inner end of the upper field is located at the lowermostend of the upper field, and the inner end of lower field is located atthe uppermost end of the lower field, and the hinge is formed by anapproximately horizontal groove.

A plastic bottle suitable for a hot-filling process in which internalvacuum is created comprising an enclosed circular base; an upper portionincluding an opening; and a body located between the base and the upperportion. The body includes a sidewall and at least one volumecompensation panel that generally deflects inwardly in response tovacuum after hot filling. The panel has an upper field, a lower field,and an interruption separating the upper field from the lower field.Each one of the upper field and the lower field forms a peak before thebottle is deformed by the vacuum, the lower field peak is locatedopposite the upper field peak relative to the interruption. Thedeformation of the panel in response to vacuum occurs in a first stage,a transition stage after the first stage, and a second stage after thetransition stage; such that: (i) in the first stage the upper field andlower field are gradually drawn inwardly in response to vacuum; (ii) thetransition stage in which at least a portion of the panel jumps from thefirst yielding stage to the second yielding stage; and (iii) in thesecond yielding stage the upper field and lower field are graduallydrawn inwardly in response to vacuum, and wherein radial height,relative to other portions of the fields, of each of the peaks isreduced upon vacuum deformation.

According to another embodiment, a plastic bottle suitable for ahot-filling process in which internal vacuum is created comprises anenclosed circular base; an upper portion including an opening; and abody located between the base and the upper portion. The body includes asidewall and at least one volume compensation panel including: an upperfield that, in longitudinal cross section, has a radial peak; a lowerfield that, in longitudinal cross section, has a radial peak; anapproximately horizontal groove, located between the upper field and thelower field, that separates the upper field peak from the lower fieldpeak; wherein radial height, relative to other portions of the fields,of each of the peaks is reduced upon vacuum deformation. A groove mayextend around the panel and merge with the sidewall. Preferably, thepeaks are distal to the upper and lower edges of the panel and each oneof the fields has a width proximate its peak that is smaller than awidth proximate the upper and lower edges of the field, whereby thepanels and groove form an hourglass shape.

The upper field preferably has a width that gradually narrows from itsupper edge to its peak and the lower field has a width gradually narrowsfrom its lower edge to its peak. A pair of opposing inclined walls mayextend from the groove along side edges of the panel generally radiallyoutwardly to side edges of the fields and to the groove.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective view of a first container illustrating a firstembodiment of the vacuum absorption panel before filling;

FIG. 2 is a first side elevational view of the container shown in FIG.1;

FIG. 3 is a second side elevational view of the container shown in FIG.2;

FIG. 4A is an enlarged longitudinal cross sectional view taken throughlines IV-IV in FIG. 2 showing the container in its as-molded state;

FIG. 4B is the longitudinal cross-sectional view shown in FIG. 4Ashowing the container in its as-molded state in dashed lines and in itsfilled & cooled or deformed state in solid lines;

FIG. 5A is a transverse cross-sectional view taken through lines V-V inFIG. 2 showing the container in its as-molded state in dashed lines andin a partially deformed state in solid lines;

FIG. 5B is a transverse cross-sectional view taken through lines V-V inFIG. 2 showing the container in its as-molded state in dashed lines andin its filled & cooled or deformed state in solid lines;

FIG. 6A is a side elevational view of a second container having a secondembodiment of the vacuum absorption panel;

FIG. 6B is a side elevational view of a variation of or modification tosecond embodiment container;

FIG. 7A is a side elevational view of the second embodiment containertaken perpendicular to the view of FIG. 6A;

FIG. 7B is a side elevational view of the second embodiment containertaken perpendicular to the view of FIG. 6B;

FIG. 8A is a transverse cross-sectional view of the second containertaken through lines VIII-VIII in FIG. 7B;

FIG. 8B is a transverse cross-sectional view of the second containertaken through lines VIII-VIII in FIG. 7B and showing the container inits as-molded and fully deformed states;

FIG. 9A is a longitudinal cross-sectional view of the second containertaken through line IX-IX in FIG. 6A;

FIG. 9B is a longitudinal cross-sectional view of the second containertaken through line IX-IX in FIG. 6A and showing the container in itsas-molded state and deformed state;

FIG. 10 is a gray-scale solid model perspective image of a thirdembodiment container; FIG. 10′ is a color solid model perspective imageof the third embodiment container;

FIG. 11 is a side elevational view of the container of FIG. 10;

FIG. 12 is a side elevational view of the container of FIG. 10 takenperpendicular to the view of FIG. 11;

FIG. 13 is a longitudinal cross-sectional view taken through lineXIII-XIII in FIG. 11 and showing the container its as-molded state anddeformed state;

FIG. 14 is a transverse cross-sectional view taken through line XIV-XIVin FIG. 11 and showing the container its as-molded state and deformedstate;

FIG. 15 is a gray-scale solid model perspective images of a fourthembodiment container; FIG. 15′ is a color solid model perspective imageof the fourth embodiment container;

FIG. 16 is an ideal graph of vacuum pressure versus deflection at thecenter of the volume compensation panel of the first embodimentcontainer shown in FIG. 1;

FIG. 17 is a calculated plot of vacuum pressure versus deflection at thecenter of a volume compensation panel of the first embodiment containershown in FIG. 1;

FIG. 18A is a plot of vacuum pressure versus deflection at the centernode of the panel of the second embodiment container shown in FIG. 6Aupon hot filling;

FIG. 18B is a plot of vacuum pressure versus container volume upon hotfilling of the second embodiment container shown in FIG. 6A;

FIG. 19A is a plot of vacuum pressure versus deflection at the centernode of the panel of third embodiment container shown in FIG. 10 uponhot filling;

FIG. 19B is a plot of vacuum pressure versus container volume upon hotfilling of the third embodiment container shown in FIG. 10;

FIG. 20 is a plot of vacuum pressure versus container volume upon hotfilling of the fourth embodiment container shown in FIG. 15;

FIG. 21A is a three dimensional plot of deformation under hot fillconditions of first embodiment container shown in FIG. 15;

FIG. 21B is a three dimensional plot of stress under hot fill conditionsof first embodiment container shown in FIG. 15;

FIG. 22A is a three dimensional plot of radial deformation under hotfill conditions of the third embodiment container shown in FIG. 10;

FIG. 22B is a three dimensional plot of overall deformation under hotfill conditions of the third embodiment container shown in FIG. 10;

FIG. 22C is a three dimensional plot of stress under hot fill conditionsof the third embodiment container shown in FIG. 10;

FIG. 23A is a three dimensional plot of radial deformation under hotfill conditions of the fourth embodiment container shown in FIG. 15;

FIG. 23B is a three dimensional plot of overall deformation under hotfill conditions of the fourth embodiment container shown in FIG. 15; and

FIG. 23C is a three dimensional plot of stress under hot fill conditionsof the fourth embodiment container shown in FIG. 15.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

This description includes four embodiments reflecting aspects of thepresent invention. The embodiments are illustrated by respectivereference numerals 10, 110, 210, and 310. As illustrated in FIG. 1through FIG. 3, container 10 according to the first embodiment includesa base 12, a body 14, an upper portion such as dome 16, and a finish 20.

Base 12 encompasses any type, and preferably includes a heel 24, astanding ring 26, and a reentrant portion 28. Preferably, an upper andlower shoulder 19 a and 19 b define a label panel. Container embodiment10 does not have a continuous waist, as it includes spaced-apart ribs 18a and 18 b in the upper and lower portions of the body 14. Body 14 maybe considered to be the portion between upper and lower waists or ribs18 a and 18 b.

Dome 16 extends upwardly from body 14 or upper shoulder 19 a. Dome 16preferably narrows to finish 20, which has threads for engaging threadson a closure 22 that covers a pour opening 21. A closure 22 forengagement with finish 18 is illustrated diagrammatically in FIG. 2.Each of the container embodiments is suitable for use with a closure.

Body 14 includes at least one volume absorption panel 30 located inbottle sidewall 32. As shown in the embodiment of FIG. 1, body 14 mayhave a pair of opposing panels 30 that are spaced 180 degrees apart.

Panel 30 includes upper and lower fields 36 a and 36 b, and a rib orgroove 38. Groove 38 functions as a hinge or trigger such that uponsufficient activation energy or upon critical portions of groove 38reaching their yield points, it yields to enable panel 30 to flex, asdescribed more fully herein. Each opposing side of panel 30 includes arim 34 that merges into container sidewall 32. Each rim 34 preferably issubstantially straight and vertical, even though the present inventionencompasses panels of any overall shape.

Each field 36 a and 36 b includes a field surface 46 (designated 46 aand 46 b to indicate the corresponding upper and lower field surfaces)and opposing transition sidewalls 48 that extend between field surfaces46 a and 46 b to container rims 34. Each field surface 46 a and 146 bpreferably is nearly flat (in transverse cross section), formed by asingle large radius, or other shape described more fully below. Thebottommost surface (in transverse cross section) of the intersection ofsidewalls 48 and rims 34 is indicated by reference numeral 44 on FIGS.5A and 5B.

Upper field 36 a has an upper wall 50 a and lower field 36 b has a lowerwall 50 b that merge respectively into upper and lower ribs, as bestshown in FIGS. 4A and 4B. Upper wall 50 a and lower wall 50 b arereferred to together as outboard walls 50. The lower part of upper field36 a and the upper part of lower field 36 b merge into groove 38. Eachfield surface 46 a and 46 b preferably has a relatively large surfacearea (compared, for example, to the surfaces of groove 38 or transitionwalls 48).

Each field surface 46 a and 46 b is wider near its outboard end (thatis, near the uppermost and lower most ends of panel 30) than near itsinboard end (that is, near the center of the panel 30) such that eachupper and lower field surface 46 a and 46 b forms an approximatelobe-shape and together approximately form an hourglass shape that isinterrupted by groove 38. As opposing rims 34 are parallel in theembodiment of FIG. 1, each transition sidewall 48 forms an approximatelytriangular shape or D-shape, although the present invention encompassesother shapes.

Groove 38 preferably is at the center of panel 30 and horizontal. Groove38 includes generally opposing groove walls 58 that are preferablystraight and that terminate at a groove bottom 60, as best shown inFIGS. 4A and 4B. Groove walls preferably form an internal angle of 120degrees, as illustrated in FIG. 4A, and preferably smoothly merges intotransition sidewalls 48 at points designated by reference numeral 64 inFIGS. 5A and 5B.

Preferably, a radial position or height (that is, the radial dimensionin transverse cross section) of each field surface 46 a and 46 b isgreater than the height of the groove bottom 60, and groove bottom 60has a radial position or height greater than rim bottom surface 44.Preferably, panel 30 is meta-stable, as described below in thediscussion of the function of panel 30.

For the particular 20 ounce container configuration shown in FIG. 1,field heights D1 and D2, which represent the heights of the(longitudinally) innermost and uppermost portions of the field surfaces46 a and 46 b, are 0.138 inches and 0.044 inches, respectively, asmeasured from a straight line between the upper and lower grooves 18 aand 18 b, as shown in FIG. 4A. The depth D3 of groove 38 (relative tosidewall 32) is approximately 0.100. The depth D4 (relative to sidewall32) of grooves 18 a and 18 b is 0.190 inches. These dimensions are notintended to limit the scope of the invention, but rather providespecific examples of structure that the inventors believe will functionas described herein.

As best shown in FIG. 3, FIG. 4A, and FIG. 4B, panel 30 preferablybulges slightly outwardly in its as-molded state when viewed inlongitudinal cross section. Preferably, panel 30 in its fully deformedstate is generally longitudinal such that field surfaces 46 areapproximately parallel. FIG. 5A shows container 10 in its as-moldedstate in dashed lines and in an intermediate state (that is, partlydeformed) under vacuum conditions and near its point of instability, asexplained more fully below, in solid lines. End points of groove 38 areindicated by reference numeral 64 in the as-molded state and byreference numeral 64′ in its intermediate or partly deformed state. FIG.5B shows container 10 in its fully deformed state in which groove ends,designated by reference numeral 64″, have yielded or buckled, alsoreferred to as jumped, such that is has reached a second point, afterwhich deformation is not non-linear. Preferably, groove bottom 60 isapproximately inline with end sidewalls 48 in the fully deformed state,as illustrated in FIG. 5B.

A container second embodiment 110 is illustrated in FIGS. 6A, 6B, 7A,7B, 8A, 8B, 9A, and 9B. The embodiment shown in FIGS. 6A and 7A isidentical to the embodiment shown in FIGS. 6B, 7B, and 8 except a centerrib is omitted from the sidewall of the latter, which is designated byreference numeral 110′, for help in illustrating the transverse crosssection. Accordingly, the description of container 110 also applies tocontainer 110′.

Container 110 includes a base 112, a body 114, an upper portion such asdome 116, a waist 118, and a finish 120. Base 112 encompasses any type,and preferably includes a heel 124, a standing ring 126, and a reentrantportion 128. Preferably, upper and lower shoulders 119 a and 119 bdefine a label panel. Dome 116 extends upwardly from body 114 or uppershoulder 119 a. Dome 116 preferably narrows to finish 120 that hasthreads for engaging threads on a closure, which is omitted from thefigures showing the second embodiment 110 for clarity.

Body 114 includes at least one volume absorption panel 130 located inbottle sidewall 132. Body 114 may have a pair of opposing panels 130that are spaced 180 degrees apart.

Panel 130 includes upper and lower fields 136 a and 136 b, and a rib orgroove 138. Groove 138 functions as a hinge or trigger such that uponsufficient activation energy or upon critical portions of groove 38reaching their yield points, it yields to enable panel 30 to flex, asdescribed more fully herein Each opposing side of panel 130 includes arim 134 that merges into container sidewall 132. Each rim 134 preferablyis substantially straight and vertical, even though the presentinvention encompasses panels of any overall shape.

Each field 136 a and 136 b includes a field surface 146 (designated 146a and 146 b to indicate the corresponding upper and lower fieldsurfaces) and opposing transition sidewalls 148 that extend betweenfield surfaces 146 a and 146 b to container rims 134. The bottommostsurface (in transverse cross section) of the intersection of sidewalls148 and rims 134 is indicated by reference numeral 144 on FIG. 8.

Upper field 136 a has an upper wall 150 a and lower field 136 b has alower wall 150 b that merge respectively into upper and portions of rim134. Upper wall 150 a and lower wall 150 b are referred to together asoutboard walls 150. The lower part of upper field 136 a and the upperpart of lower field 136 b merge into groove 138. Each field surface 146a and 146 b preferably has relatively large surface area (compared, forexample to the surfaces of groove 138 or transition walls 148).

Each field surface 146 a and 146 b is wider near its outboard end (thatis, near the uppermost and lower most ends of panel 130) than near itsinboard end (that is, near the center of the panel 130) such that eachupper and lower field surface 146 a and 146 b forms an approximatelobe-shape and together approximately form an hourglass shape that isinterrupted by groove 138. As opposing rims 134 are parallel in theembodiment of FIG. 1, each transition sidewall 148 forms anapproximately triangular shape or D-shape, although the presentinvention encompasses other shapes.

Groove 138 preferably is at the center of panel 30 and horizontal.Groove 138 includes generally opposing groove walls 158 that arepreferably straight and that terminate at a groove bottom 160, as bestshown in FIG. 8. Groove walls preferably form an internal angle of 120degrees in transverse cross section, but the present inventionencompasses any configuration. Groove 138 preferably smoothly mergesinto transition sidewalls 148 at points designated by reference numeral164.

Container 110 has a volumetric capacity of 20 ounces; the heights anddepths of panel 130 are approximately those provided for firstembodiment container 10. Referring to FIGS. 8A, 8B, 9A, and 9B toillustrate additional dimensions and relationships, dimension D5 betweensurface 144 and groove bottom 160 is 0.090 inches. The vertical portionsof transition wall 148 form an angle A2 of 35 degrees from a referenceline equidistant between opposing panels 130 or parallel to groove 138.Transition wall 148 and vertical rim 134 form an internal angle A3 of 85degrees. The upper and lower portions of rim 134 approximately form anangle A4 of 60 degrees relative to a vertical reference line.

As best shown in FIG. 9A, groove walls 158 form an internal angle A5 of120 degrees. Groove 138 preferably has a radius R1 of 0.20 inches at itsbottom 160 and a radius R2 of 0.50 inches between groove walls 158 andfield surfaces 146 a and 146 b. Each field surface 146 a and 146 b isformed by a single radius R3 of approximately 9.4 inches. The presentinvention encompasses field surfaces 146 a and 146 b (and of the otherembodiments described herein) having shapes, in transverse crosssection, other than a single radius, including being flat orapproximately flat, having a radius that changes gradually or at aconstant rate, or several radiuses that merge.

FIG. 8 b and FIG. 9B illustrate container 110 in its as-mold state insolid lines and in its deformed state under normal vacuum conditionsassociated with hot filling in dashed lines. Panel 130 preferably bulgesslightly outwardly in its as-molded state when viewed in longitudinalcross section. Preferably, panel 130 in its fully deformed state isgenerally longitudinal such that field surfaces 146 a and 146 b areapproximately parallel. In its deformed state, groove ends 64″preferably are line with groove bottom 60.

A container third embodiment 210 is illustrated in FIGS. 10, 11, 12, 13and 14. Container 210 includes a base 212 a body 214, an upper portionsuch as dome 216, a waist 218, and a finish 220 (not shown in figuresfor third embodiment container 210).

Base 212 encompasses any type, and preferably includes a heel 224, astanding ring 226, and a reentrant portion 228. An upper and lowershoulder 219 a and 219 b define a label panel. Dome 216 extends upwardlyfrom body 214 or upper shoulder 219 a. Dome 216 preferably narrows tofinish 220 that has threads for engaging threads on a closure 222.

Body 214 includes at least one volume absorption panel 230 located inbottle sidewall 232. Body 214 may have a pair of opposing panels 230that are spaced 180 degrees apart.

Panel 230 includes upper and lower fields 236 a and 236 b, a horizontalrib or groove 238 separating the fields, and a vertical groove 239. Eachopposing side of panel 230 includes a rim 234 that merges into containersidewall 232. Each rim 234 preferably is substantially straight andvertical, even though the present invention encompasses panels of anyoverall shape.

Each field 236 a and 236 b includes a field surface 246 (designated 246a and 246 b to indicate the corresponding upper and lower fieldsurfaces) and opposing transition sidewalls 248 that extend betweenfield surfaces 246 a and 246 b to container rims 234. The bottommostsurface of the intersection of sidewalls 248 and rims 234 is indicatedby reference numeral 244 on FIG. 14.

Upper field 236 a has an upper wall 250 a and lower field 236 b has alower wall 250 b that merge respectively into upper and portions of rim234. Upper wall 250 a and lower wall 250 b are referred to together asoutboard walls 250. The lower part of upper field 236 a and the upperpart of lower field 236 b merge into groove 238. Each field surface 246a and 246 b preferably has relatively large surface area (compared, forexample to the surfaces of groove 238 or transition walls 234).

Each field surface 246 a and 246 b is wider near its outboard end (thatis, near the uppermost and lower most ends of panel 230) than near itsinboard end (that is, near the center of the panel 230) such that eachupper and lower field surface 246 a and 246 b forms an approximatelobe-shape and together approximately form an hourglass shape that isinterrupted by groove 238. As opposing rims 234 are parallel, eachtransition sidewall 248 forms an approximately triangular shape orD-shape, although the present invention encompasses other shapes.

Groove 238 preferably is at the center of panel and horizontal. Groove238 includes generally opposing groove walls 258 that are preferablystraight and that terminate at a groove bottom 260. Groove wallspreferably form an internal angle of 120 degrees in transverse crosssection, but the present invention encompasses any configuration. Groove238 preferably smoothly merges into transition sidewalls 248 at pointsdesignated by reference numeral 264.

Container 210 has a volumetric capacity of 20 ounces and the panel 230dimensions may be approximately the same as those of second embodimentcontainer 110. FIG. 13 and FIG. 14 illustrate container 210 in itsas-mold state in solid lines and in its deformed state under normalvacuum conditions associated with hot filling in dashed lines. Panel 230preferably bulges slightly outwardly in its as-molded state and isconcave in its fully deformed state when viewed in when viewed inlongitudinal cross section. Panel 230 in its fully deformed state isconcave when viewed in transverse cross section.

Groove 38 functions as a hinge or trigger such that, upon sufficientactivation energy or upon critical portions of groove 38 reaching theiryield points, it yields to enable panel 30 to flex, as described morefully herein. Vertical groove 239 preferably is equidistant from grooveends 264 and perpendicular to the longitudinal axis of groove 238.Groove 239 extends into fields 246 a and 246 b and, preferably, does notextend fully to the upper and lower portions of rim 234.

To achieve the concave shape, vertical groove 239 may act as a hinge orlower the activation energy required for panel 230 to reach the yieldingor buckling stage. In some embodiments, small regions of panel 230 neargroove ends 264 are high stress regions that reach their yield pointsand buckle to enable the overall panel perform as described herein.

A container fourth embodiment 310, illustrated in FIG. 15, has the samestructure as third embodiment container 210 in its base 312, dome 316,waist 318, finish 320, and sidewall 32. Its panels 330 have the same rim334 and transition sidewalls 348 as third embodiment container 210 suchthat fields 346 a and 346 b have the same outline shape as that of thirdembodiment panels 230.

Each panel 330 includes a pair of groove segments 328 a and 328 b.Outboard ends 364 of groove segments 238 a and 238 b merge smoothly intotransition sidewalls 348. Segments 328 a is spaced apart from segment328 b by an intermediate space 329 that merges smoothly into fields 349a and 349 b.

Preferably the bottle sidewall for each embodiment (that is, sidewalls32, 132, 232, and 232) is generally cylindrical with horizontal ribs;the invention encompasses sidewalls of any shape. The present inventionis not limited to a particular number of panels, nor to their size,overall shape, or relative spacing about the container's circumference.The number of panels may be chosen according to well-known parametersthat will be understood by persons familiar with hot-fill bottletechnology upon reading the present disclosure. Also, the bodies of eachembodiment may include additional structure, including but not limitedto conventional or other panels not covered by the present invention.

The disclosed dimensions and angles are not intended to limit the scopeof the invention, but rather provide specific examples of structure. Thepresent invention is not limited to a particular configuration orgeometries, but rather the scope is controlled by the language of theclaims Variations in the components are encompassed by the presentinvention, as will be understood by persons familiar with bottleengineering and manufacturing upon considering this disclosure.

Preferably, containers 10, 110, 210, and 310 are formed of aconventional PET, and any other suitable material is contemplated. Thecontainer embodiments having the features described herein may be formedof a relatively thinner sidewall. The thin sidewalls, in somecircumstances, may aid in the yielding (including reaching the elasticlimit of the material or other modes of giving way) of portions of thecontainers (such as at intersections 64, 164, 264, and 364).Accordingly, the present panels are suitable for lightweight containers.

The following description of the operation refers to components of firstembodiment container 10 for convenience, but is equally applicable tothe function of containers 110, 210, and 310 unless stated otherwise.After container 10 is fill with a liquid product at an elevatedtemperature, such as 185° F., it is sealed and capped by closure 22.During subsequent cooling, the liquid product and any air in theheadspace between the liquid and the seal cools and contracts. Theplastic material of container 10 may also undergo shrinkage that reducesits volume, but the container shrinkage is typically small compared tothe product and headspace gas shrinkage. Accordingly, an internalnegative pressure acts on container 10.

FIG. 16 is an ideal graph of internal container pressure versus themagnitude of inward deflection of the center node (such as in thegeometric center of groove 38) of a panel, such as panel 30, toillustrate the function of the panels disclosed herein. As used herein,“stiffness” generally refers to mechanical stiffness, and moreparticularly is defined as the local slope of the pressure versusdeflection curve, such as the ideal curve shown in FIG. 16.

The panel undergoes at least three distinct stages of deformation: apre-yield stage, a yielding stage, and a post-yield stage. The termyield, as used herein, encompasses buckling—that is, relatively suddenmovement from one state or position to another state or position—and aslow progression from one state or position to another state orposition. The containers described herein may function as describedherein, it is surmised, because a portion of the panel material (such asnear groove end 64, 164, 264, and 364) reaches a yield point on thestress-strain curve such that the portion reaches its elastic limit; thepresent invention is not limited to structure that functions accordingto this principle, but also encompasses the other means for enabling thepanel to give way in a manner in which no portion of the structurereaches its yield point. Further, the present invention encompasses thestructure defined in the claims, regardless of its function.

During the pre-yield stage or pre-buckling stage, which is identified byreference letter A in the idealized chart in FIG. 16, a portion of thepanel builds up activation energy in preparation of yielding. During thepre-yielding stage, the panel exhibits a constant stiffness modulusM_(A) or a stiffness that only changes slightly. When used to refer tostiffness, the term “constant” encompasses some variation is thelinearity of a plot as long as it is reflected by a smooth and gentlecurve.

During the yielding stage, which is indicated by region B in FIG. 16, aportion of the panel buckles or in some other way yields, and the panelexhibits a constant stiffness modulus M_(B) or a stiffness that onlychanges slightly. During the post-yield stage, which is identified byreference letter C in FIG. 16, the yielding portion has released itsactivation energy, and the panel exhibits a constant stiffness modulusM_(C) or a stiffness that only changes slightly.

FIG. 17 is a calculated plot of internal bottle pressure versusmagnitude of inward deflection of a center node—that is, a geometriccenter of groove 38—of container 10 having panels 30 as described aboveupon hot filling and subsequent cooling. The calculations were performedusing finite element analysis. The center node was chosen to isolate thefunction of panel 30 while the entire container undergoes vacuumabsorption. In an initial stage, which is designated by reference letterI₁, the inventors theorize that various portions of the container, suchas (possibly) portions of the dome 16, sidewalls 32, bottom 214, andfields 46 a and 46 b, deform with little inward deformation of thecenter node. Alternatively, panel 30 may function as a conventionalpanel during this initial stage.

At point p₁, the pre-yield stage B₁ begins, in which the predominantvacuum absorption mechanism is inward deflection of panel 30, which isevident by the lower slope manifested in stiffness modulus M_(B1). Eventhough it is likely or possible that the mechanisms of initialdeflection stage I₁ are at least somewhat still present in pre-yieldstage B₁, modulus M_(B1) is approximately constant.

The inventors theorize that during pre-yield stage B₁, groove end walls64 deflect as shown in FIG. 5A. Calculated stress is high near theintersection of groove 38 and transition sidewalls 34, as illustrated inthe three dimensional plot of stress in FIG. 21B. The intersection isdesignated by reference numeral 64 in the as-molded, undeformed bottle.

FIG. 5A, which shows groove 38 during pre-yield stage B₁, shows thecalculated deformation of groove 38 and the movement of groove end walls62 relative to groove bottom 60. In general, the extent of yielding orbuckling can control the magnitude of volume compensation, as thelocalized zone of deformation enables larger deformation of the panel.The inventors theorize that local stress at intersections 64 continuesto rise (which is also generally referred to as rising activationenergy) until reaching the yield stress of the material, at which pointq₁ the yielding stage C₁ begins.

During yielding stage C₁, FIG. 17 illustrates that a large amount ofcenter node deflection occurs relative to vacuum absorption. Theinventors theorize that the portions of container 10 proximateintersections 64, upon reaching the elastic limit of its material,yield. The yielding may be sudden, generally referred to herein asbuckling, or a slow giving way.

FIG. 5B illustrates groove 38 after yielding has occurred, such as atpoint r₁ in FIG. 17. The solid line illustrating groove 38 shows portion64″ as a substantially straight portion between transition wall 34 andgroove bottom 60, reflecting not only the inward movement of groovebottom 60, but also the overall change in shape of groove 38 andtransition wall 34.

FIGS. 18A and 18B provide plots of vacuum pressure versus magnitude ofcenter node deflection and vacuum pressure versus container volumechange for second embodiment container 110 upon hot filling andsubsequent cooling. FIGS. 19A and 19B provide vacuum pressure versusmagnitude of center node deflection and vacuum pressure versus containervolume change for third embodiment container 210 upon hot filling andsubsequent cooling. FIG. 20 provides vacuum pressure versus containervolume change for fourth embodiment container 310 upon hot filling andsubsequent cooling.

FIG. 21A and FIG. 21B provide a three dimensional deformation plot andstress plot, respectively, of first embodiment container 10 upon hotfilling. FIGS. 22A and 22B provide, for third embodiment container 210,three dimensional plots of radial displacement and displacement, andFIG. 22C provides a three dimensional plot of stress upon hot filling.FIGS. 23A and 23B provide, for fourth embodiment container 310, threedimensional plots of radial displacement and displacement, and FIG. 23Cprovides a three dimensional plot of stress for hot filling

The description of the function of the container embodiments is directedto preferred embodiments of the structure and function of the presentinvention, but as is clear from the above description, the invention isnot limited to the particular disclosed structure and function. Rather,the scope of the invention should be defined by the language ofallowable claims.

1. A plastic bottle suitable for hot-filling, said bottle comprising: anenclosed circular base; an upper portion including an opening; and abody disposed between the base and the upper portion, the body includesa sidewall and at least one volume compensation panel that generallydeflects inwardly in response to negative pressure after hot filling,wherein during a pre-yielding stage, the vacuum panel deflects inwardlyat a first stiffness and, during a post-yielding stage, the vacuum paneldeflects inwardly at a second stiffness
 2. The bottle of claim 1 whereina portion of the panel yields during the inward deflection, therebyfacilitating a change in stiffness.
 3. The bottle of claim 2 wherein thefirst stiffness does not equal the second stiffness.
 4. The bottle ofclaim 1 wherein the yielding stage includes buckling.
 5. The bottle ofclaim 1 wherein each one of the vacuum panels includes a groove disposedbetween a pair of fields.
 6. The bottle of claim 5 wherein a portion ofthe groove slowly gives way during said inward deflection, therebyfacilitating the stiffness variation.
 7. The bottle of claim 5 wherein aportion of the groove buckles during said inward deflection, therebyfacilitating the stiffness variation.
 8. The bottle of claim 7 whereineach one of the vacuum panels further includes: a pair of opposing rimwalls, each one of the rim walls is disposed proximate a correspondingedge of the body sidewall, a pair of raised fields disposed within saidedge, and a groove disposed between the fields.
 9. The bottle of claim 8wherein a bottom of the groove is higher than a bottom of the rim walls,and each one of an uppermost portion of the fields is higher than thebottom of the groove.
 10. The bottle of claim 9 wherein the grove has apair of opposing end walls that extend inwardly from the groove bottomto the rim walls.
 11. The bottle of claim 9 wherein the end walls bucklein response to the negative pressure.
 12. The bottle of claim 11 whereinsaid buckling enables inward movement of the groove.
 13. The bottle ofclaim 1 wherein the groove extends approximately from one of the rimwalls approximately to the opposing rim.
 14. The bottle of claim 1wherein the body further includes one or more vacuum panels.
 15. Aplastic bottle suitable for hot-filling, said bottle comprising: anenclosed circular base; an upper portion including an opening; and abody disposed between the base and the upper portion, the body includesa sidewall and at least two volume compensation panels that deflectinwardly after hot-filling, each one of the panels including an upperfield, a lower field, and a rib that is disposed between the upper andlower fields and that includes an oblique portion that buckles duringthe volume compensation process, said buckling facilitating inwardmovement of the upper and lower fields changes the stiffness from apre-buckling value to a post-buckling value.
 16. The bottle of claim 15wherein the oblique portion of the rib is located at an end of a bottomof the rib.
 17. The bottle of claim 16 wherein the oblique portion formsan oblique angle with a bottom of the rib and is not tangential to thebody sidewall.
 18. The bottle of claim 16 wherein the rib has sidewallsthat extend upwardly from the rib bottom and connect to the fields. 19.The bottle of claim 18 wherein the fields have an approximately flatsurface.
 20. A method of absorbing negative pressure within a hot-filledplastic bottle, the method comprising the steps of: (a) providing abottle having: an enclosed circular base; an upper portion including anopening; and a body disposed between the base and the upper portion, thebody includes a sidewall and at least two volume compensation panels,(b) filling the bottle with a (liquid) product at an elevatedtemperature and sealing (capping) the opening; and (c) at least aportion of the panels deflecting inwardly after the filling and sealingstep (b) in response to negative pressure within the bottle, said inwarddeflection includes a first main stage wherein the volume compensationpanels exhibit a first stiffness and a second main stage wherein thevolume compensation panels exhibit a second stiffness.
 21. The method ofclaim 20 wherein providing step (a) includes providing a bottle in whicheach of the vacuum panels includes a rib disposed between opposingfields.
 22. The method of claim 21 wherein the rib undergoes a change inshape between the first and second main stages of the deflecting step(c).
 23. The method of claim 21 wherein the rib undergoes bucklesbetween the first and second main stages of the deflecting step.
 24. Themethod of claim 19 wherein each one of the vacuum panels includes agroove disposed between a pair of fields.
 25. The method of claim 24wherein a portion of the groove buckles during said inward deflection,thereby facilitating the transition form the first stiffness to thesecond stiffness.
 26. The method of claim 25 wherein each one of thevacuum panels further includes: a pair of opposing rim walls, each oneof the rim walls is disposed proximate a corresponding edge of the bodysidewall, a pair of raised fields disposed within said edge, and agroove disposed between the fields.
 27. The method of claim 26 wherein abottom of the groove is higher than a bottom of the rim walls, and eachone of an uppermost portion of the fields is higher than the bottom ofthe groove.
 28. The method of claim 27 wherein the grove has a pair ofopposing end walls that extend inwardly from the groove bottom to therim walls.
 29. The method of claim 27 wherein the end walls buckle inresponse to the negative pressure.
 30. The method of claim 29 whereinsaid buckling enables inward movement of the groove.
 31. A plasticbottle suitable for a hot-filling process in which internal vacuum iscreated, said bottle comprising: an enclosed circular base; an upperportion including an opening; and a body disposed between the base andthe upper portion, the body includes a sidewall and at least one volumecompensation panel that generally deflects inwardly in response tovacuum after hot filling, the panel having an upper field, a lowerfield, and a hinge located between the upper and lower fields, whereindeformation of the panel in response to vacuum occurs in a first stage,a transition stage after the first stage, and a second stage after thetransition stage; such that: (i) in the first stage the upper field andlower field are gradually drawn inwardly in response to vacuum; (ii) thetransition stage is unstable such that at least a portion of the paneljumps from the first yielding stage to the second yielding stage; and(iii) in the second yielding stage the upper field and lower field aregradually drawn inwardly in response to vacuum.
 32. The bottle of claim1 wherein each of the upper field and the lower field have an inner endlocated proximate the hinge and an outer end located distal from thehinge, and the inward deformation of each field inner end is greaterthan the deformation of the each field outer end.
 33. The bottle ofclaim 32 wherein the inward deformation of each field inner end isgreater than the deformation of the each field at its longitudinalcenter.
 34. The bottle of claim 32 wherein, in longitudinal crosssection, a line between the upper field outer end and the upper fieldinner end forms an internal angle with a line between the lower filedouter end and the upper field inner end, and the angle is less than 180degrees.
 35. The bottle of claim 34 wherein the angle goes toapproximately 180 degrees after vacuum deformation is complete.
 36. Thebottle of claim 34 wherein the angle goes to greater than 180 degreesafter vacuum deformation is complete.
 37. The bottle of claim 32 whereinthe inner end of the upper field is located at the lowermost end of theupper field, and the inner end of lower field is located at theuppermost end of the lower field.
 38. The bottle of claim 32 wherein thehinge is formed by an approximately horizontal groove.
 39. The bottle ofclaim 32 wherein each one of the upper field and the lower field formsan approximately straight line in longitudinal cross section through thecenter of the panel.
 40. The bottle of claim 32 wherein each field has alobe-like shape.
 41. A plastic bottle suitable for a hot-filling processin which internal vacuum is created, said bottle comprising: an enclosedcircular base; an upper portion including an opening; and a bodydisposed between the base and the upper portion, the body includes asidewall and at least one volume compensation panel that generallydeflects inwardly in response to vacuum after hot filling, the panelhaving an upper field, a lower field, and an approximately horizontalgroove between the upper field and lower field, wherein deformation ofthe panel in response to vacuum occurs in a first stage, a transitionstage after the first stage, and a second stage after the transitionstage; such that: (i) in the first stage the upper field and lower fieldare gradually drawn inwardly in response to vacuum; (ii) the transitionstage in which at least a portion of the panel jumps from the firstyielding stage to the second yielding stage; and (iii) in the secondyielding stage the upper field and lower field are gradually drawninwardly in response to vacuum.
 42. The bottle of claim 41 wherein eachone of the upper field and the lower field merge into the groove. 43.The bottle of claim 41 wherein, in longitudinal cross section, thegroove has a curved lower wall and a pair of opposing walls.
 44. Aplastic bottle suitable for a hot-filling process in which internalvacuum is created, said bottle comprising: an enclosed circular base; anupper portion including an opening; and a body disposed between the baseand the upper portion, the body includes a sidewall and at least onevolume compensation panel that generally deflects inwardly in responseto vacuum after hot filling, the panel having an upper field, a lowerfield, and an interruption separating the upper field from the lowerfield; each one of the upper field and the lower field forming a peakbefore the bottle is deformed by the vacuum, the lower field peak islocated opposite the upper field peak relative to the interruption;wherein deformation of the panel in response to vacuum occurs in a firststage, a transition stage after the first stage, and a second stageafter the transition stage; such that: (i) in the first stage the upperfield and lower field are gradually drawn inwardly in response tovacuum; (ii) the transition stage in which at least a portion of thepanel jumps from the first yielding stage to the second yielding stage;and (iii) in the second yielding stage the upper field and lower fieldare gradually drawn inwardly in response to vacuum, and wherein radialheight, relative to other portions of the fields, of each of the peaksis reduced upon vacuum deformation.
 45. A plastic bottle suitable for ahot-filling process in which internal vacuum is created, said bottlecomprising: an enclosed circular base; an upper portion including anopening; and a body disposed between the base and the upper portion, thebody includes a sidewall and at least one volume compensation panelincluding: an upper field that, in longitudinal cross section, has aradial peak; a lower field that, in longitudinal cross section, has aradial peak; an approximately horizontal groove, located between theupper field and the lower field, that separates the upper field peakfrom the lower field peak; wherein radial height, relative to otherportions of the fields, of each of the peaks is reduced upon vacuumdeformation.
 46. The bottle of claim 45 wherein includes a grooveextending around the panel and merging with the sidewall.
 47. The bottleof claim 46 wherein the peaks are distal to the upper and lower edges ofthe panel.
 48. The bottle of claim 47 wherein each one of the fields hasa width proximate its peak that is smaller than a width proximate theupper and lower edges of the field, whereby the panels and groove forman hourglass shape.
 49. The bottle of claim 48 wherein the upper fieldhas a width that gradually narrows from its upper edge to its peak andthe lower field has a width gradually narrows from its lower edge to itspeak
 50. The bottle of claim 49 wherein includes a groove extendingaround the panel and merging with the sidewall.
 51. The bottle of claim50 wherein a pair of opposing inclined walls extend from the groovealong side edges of the panel generally radially outwardly to side edgesof the fields and to the groove.